Mars Curiosity Rover's landing explained

Earlier I linked to an animation of the planned landing of the Mars Curiosity Rover landing. It involved a complex series of steps involving parachutes and a rocket that lowered the Rover to the ground on the end of a cable.

Above is a video in which engineers explain the various stages of the landing, and why they are doing it in such a complex manner. It all boils down to the difficulty of landing such a heavy and delicate machine in the thin Martian atmosphere.

As an aside, they stress that everything needs to go precisely as planned, so I found it a little alarming that they screwed up their subtitles starting at the half-way mark. I know it was a graphics agency and not the engineering department that put the video together, but still...